High power traveling wave tube



Sept. 17, 1963 R. w. WILMARTH HIGH POWER TRAVELING WAVE TUBE Filed April 6, 1960 4 0 0 O Q QO Q 0 0 0 0 0 0u0u0 0 0 0 0 0 0 0 0 0 INVEN TOR R0554? WMMART/l GK 5 a 00000000000000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0000000000 000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 000000000000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 w! I m m. w .3 3 W m Q\\\\\\\\\\\\\\\\\\\\\-w m u A M. \& m Q .=\\I\-\\\\\\-!i\\\\-:inlx\\\\..t uwWSKUQQK .w w w\ M W \1 WER .Gfixokq mm K W 5 v ms 3 \xQ No Q l A 000000000000000000000000000000000000000000 0 0 0 0 0 0 0 0 0 w0$ 00000000000a$0 0wwwwwwwwwwwwwwwwwwwM m, w 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0/ 0000000000000000000000000000 0 00000 0 0 0 0 0 0 0 0 0 0 0 0 00000000000000000000000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00000000000000000000 00 000007 0.0w00-w0" wwwvvvwww$0www wwwwwvwvwwvvvw vvwwu W AGENT United States Patent 3,104,344 HIGH POWER TRAVELTNG WAVE TUBE Robert W. Wilmarth, Bloomfield, Ni, assignor to International Telephone and Telegraph Corporation, Nutley, N.J., a corporation of Maryland Fiied Apr. 6, 1969, er. No. 20,497 Claims. (62. 31539.3)

This invention relates to beam tubes, and more particularly to traveling wave tubes and the like, wherein a focussed beam of electrons interacts with the electric fields of high frequency waves to produce amplification of the waves.

In known traveling wave tubes, it has been customary to provide an electron beam collector for a magnetically focussed beam, as a separate and distinct structure, independent of the slow wave propagation circuit as well as the input and output matching wave guides.

Attempts have been made to achieve smaller and simpler beam tubes. Particularly in high power traveling wave tubes, it also has been a problem to provide easy assembly without degradation of radio performance of the slow wave propagating structure and associated wave guide circuits.

An object or" the invention is to utilize a wave guide in a high power traveling wave tube both as the collector for the electron beam and as the output for the amplified waves.

Another object of the invention is to match the impedance of such a wave guide beam collector with the impedance of the slow wave propagating structure in a traveling wave tube.

A feature of the invention is a wave guide closed at one end and utilized as a combined high power beam collector and radio frequency output, subsequent to the beams interaction with the slow wave structure and to its defocussing.

Another feature of the invention is a choke section connector located between the wave guide beam collector and the slow wave structure to permit ease of assemblage and provide a good radio frequency connection therebetween.

Another feature of the invention is a wave guide collector for a focussed beam, which extends lengthwise beyond the range of the focussing field.

In accordance with the invention, a single wave guide section serves both as an electron beam collector and combined radio frequency output for high power traveling wave tubes, collecting the spreading electrons in its side walls, after the beam is defocussed. The wave guide collector, aligned with the slow wave propagating structure extends beyond the field of the beam focussing magnetic solenoid, whereby the spreading electron beam is absorbed by the side walls of the collector guide. Heat engendered by the absorbed electron beam is dissipated by the collector wave guide without degrading the performance of the radio frequency circuit.

Also, the wave guide collector permits an easy stackable construction of the tube, whereby the slow wave structure, the collector and wave guide transitions in the radio frequency circuit are easily aligned and assembled by choke coupling connectors. The aligning assembly likewise permits the easy and close fitting of the magnetic focussihg solenoid onto the beam tube in closest proximity to the electron beam, whereby a lighter and more economical solenoid construction is possible.

The above-mentioned and other features and objects of the invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawing, in which:

The FIGURE is a longitudinal sectional view of a trav- 3,104,344 Patented Sept. 17, 1963 eling wave tube in accordance with an embodiment of the invention.

Referring now to the figure of the drawing, the traveling wave tube 1 has an evacuated metallic envelope 2 with an electron gun 3 at one end thereof, for shaping an electron stream into a beam. The beam is focussed along the axis of the tube 1 by the magnetic field of solenoid 5, energized by a current source (not shown) to provide a longitudinal magnetic focussing field to confine the electrons into a narrow beam. From the cathode emissive surface 6 electrons are drawn to anode electrode 7, and shaped as a stream by the configuration of the electron gun 3. The beam passes thru apertured ferrule 8, into a radio frequency section which includes the rectangular to circular wave guide. transition 16, slow wave structure 9, and wave guide collector 10*.

The magnetically focussed electron beam interacts with HF. or microwave energy applied to slow wave structure 9 from an input coaxial line 19, whose inner conductor 25 terminates in a radiating element 24 A coaxial seal 26 of glass or ceramic serves to insulate the inner conductor 25 from the outer conductor of coaxial line 19.

The slow-wave structure 9 is coupled at its output end, to a longer section of circular wave guide 1%, while at its input end, the slow wave structure 9, is coupled to a shorter section of wave guide 13. The electron gun 3-, the slow wave structure 9, the wave guide collector 10 and the wave guide section 13 are all in line arranged around a common central axis.

Due to the shorter length of magnetic solenoid 5 with respect to the length of tube 1, the high power electron beam is only focussed in its passage from anode 7 thru the slow wave structure 9. Subsequent to its exit from the slow wave structure 9, the electron beam is allowed to spread along the length of wave guide 10, whence the electrons are collected on the interior walls thereof. Since the wave guide 10 is relatively large in cross-section, it permits rapid cooling of the surface heated by the absorbed electron beam. Cooling fins, water jackets and the like may be applied to the exterior surface of collector 10 to enhance the cooling effect.

The slow-wave structure 9 is matched in impedance over a wide band to the aligned sections of wave guide 10, 13 by means of an iris matching device 15. The matching discs 15 are brazed in position at the opposite ends of the slow wave structure 9 and between the choke sections 11, 12. The choke sections 11, 12 effect good electrical coupling to the input and output waveguides 13, 10 without the necessity of brazes thereto.

Microwave energy which is applied to the input coaxial line 19 propagates from radiating element 26 into an apertured rectangular to circular wave guide transition 16 and thence is transmitted thru circular wave guide sections 10, 13. The aperture in the waveguide transition 16 allows the focussed beam to pass thru the slow wave structure 9, where microwave energy interacts with the electron beam to provide amplification in the well known manner.

The amplified microwave energy is derived at the output end 18 of Wave guide 10 thru a similar wave guide transition 17, which is sealed by an offset wave guide window 24-. An advantage of this ofiset arrangement is that the window 24 is not subjected to direct electron bombardment from the spreading electron beam, which is mainly collected at the sidewalls of wave guide 10 and partially on the end wall 21 of the rectangular wave guide transition 17.

For the purpose of facilitating stacking assembly of the wave guides to the slow wave structure 9, choke sections 11, 12, are interposed in the circular wave guides 10, 13, permitting the parts to be slid together and secured with heliarc welds 27. The choke sections 11, 12, provide a smooth electrical continuation of the wave guide surfaces 10, 13, without leakage of wave energy and so a good transfer of microwaves is .thereby provided. Also, the choke sections provide an easy assembly of the slow wave structure 9 to wave guides 10, 13. In one par-ticular embodiment, a slow wave structure 9 of the clover leaf type was used with a matching iris 15 having an elliptical opening, but it should be apparent that other well-known types of slow wave interaction circuit may be utilized.

While my invention has been illustrated in connection with a particular embodiment, it should be distinctly understood that various modifications and applications of my invention will occur to those skilled in the art. The particular embodiment is given merely as an example and is not to be considered as a limitation on my invention as set forth in the objects thereof and in the accompanying' claims.

What is claimed is: V

1. A beam tube comprising'an electron beam source for directing a beam along a given path, means for focus sing the beam, a slow wave propagating structure extending within said focussing means along and adjacent to said path for providing electromagnetic interaction between the electrons of said beam and electromagnetic waves propagated along said structure, input wave guide means for applying electromagnetic waves to one end of said slow wave propagating structure, and output wave guide means aligned with and coupled to said slow Wave structure at the other end for collecting said electrons from said beam, said output wave guide including means offset from the path of said beam for deriving output energy from said electromagnetic waves.

2. The beam tube of claim 1, wherein impedance matching and coupling means are connected at each end between said slow wave structure and said Wave guides.

3. The beam tube of claim 2, wherein said output wave guide means extends beyond said focussing means to permit the beam to spread after interaction with said waves and be collected along the walls thereof.

4. The beam tube of claim 3, wherein said output wave guide has a closed end beyond said focussing means, said closed end including a window offset from said beam in a vertical path for deriving said output energy.

5. The beam tube of claim 4, wherein said impedance matching and coupling means includes an apertured iris and choke section.

6 The beam tube of claim 5, wherein wave guide transition sections are connected to saidinput wave guide and at said closed end.

7. The beam tube of claim 6, wherein said wave guide transition sections connect from rectangular to circular sections, and a coaxial radiating probe is connected to said input transition section for input of electromagnetic waves thereto.

8. A high frequency electronic amplifier comprising an electron beam source, means for directing the beam along a given path, means for focussing the electron beam, a slow wave propagating structure extending within said focussing means along said path for providing electromagnetic interaction between the electrons of said beam and electromagnetic waves propagated along said structure, input means for applying electromagnetic waves to one end of said slow wave propagating structure, a 7

wave guide beam collector aligned with and coupled to said slow Wave structure at the other end for collecting said electrons, said wave guide collector extending beyond said focussing means and'including output coupling means for deriving said amplified waves said output coupling being axially displaced from and perpendicular tothe path of said beam. 7

9. The high frequency electronic amplifier of claim 8, wherein said input means comprises a coaxial line having the inner conductor terminating in a radiating device. 0 v, 10. The high frequency electronic amplifier of claim 8, wherein rectangular to circular wave guide transitions and impedance matching wave guide sections couple said slow wave structure to said input and output means.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A BEAM TUBE COMPRISING AN ELECTRON BEAM SOURCE FOR DIRECTING A BEAM ALONG A GIVEN PATH, MEANS FOR FOCUSSING THE BEAM, A SLOW WAVE PROPAGATING STRUCTURE EXTENDING WITHIN SAID FOCUSSING MEANS ALONG AND ADJACENT TO SAID PATH FOR PROVIDING ELECTROMAGNETIC INTERACTION BETWEEN THE ELECTRONS OF SAID BEAM AND ELECTROMAGNETIC WAVES PROPAGATED ALONG SAID STRUCTURE, INPUT WAVE GUIDE MEANS FOR APPLYING ELECTROMAGNETIC WAVES TO ONE END OF SAID SLOW WAVE PROPAGATING STRUCTURE, AND OUTPUT WAVE GUIDE MEANS ALIGNED WITH AND COUPLED TO SAID SLOW WAVE STRUCTURE AT THE OTHER END FOR COLLECTING SAID ELECTRONS FROM SAID BEAM, SAID OUTPUT WAVE GUIDE INCLUDING MEANS OFFSET FROM THE PATH OF SAID BEAM FOR DERIVING OUTPUT ENERGY FROM SAID ELECTROMAGNETIC WAVES. 